Directions

Place the butter, sugar, salt, and vanilla into the bowl of a stand mixer with the paddle attachment. Mix at low speed. When combined, add egg white then barely incorporate the flour.

Divide the mixture in half. Add the cocoa powder to one half and the cornstarch to the other half. Place each batter a separate pastry bag, then place both bags inside a larger pastry bag fitted with a 3/4-inch star tip.